Portable, wheeled tool carts have been available for some time. One such prior art tool cart is shown and described by Wise, the inventor herein, in U.S. Pat. No. 5,642,898 issued Jul. 1, 1997. Additional tool carts have been described in the patent literature. For instance, U.S. Pat. No. 4,955,941, issued Sep. 11, 1990, to Rousseau, describes a support table for a bench saw. U.S. Pat. No. 4,230,329, issued Oct. 28, 1980 to Johnson, describes a mobile cart. U.S. Pat. No. 5,161,590, issued Nov. 10, 1992, to Otto, describes a miter saw table apparatus. U.S. Pat. No. 5,255,724; issued Oct. 26, 1993, to Butke, describes an adjustable extension assembly. A brochure showing the Rousseau SS2850 product discloses a mobile miter saw stand. U.S. Pat. No. 6,886,836 entitled “Counterbalanced Universal Mobile Saw Stand,” issued May 3, 2005 to the inventor herein discloses a built-in handtruck design that enables the end user to transport common table saws and equipment to the location of the project being undertaken. The unit quickly folds out into a fully supporting work bench for actual use of the saw and/or equipment. The saw stand shown in the '836 patent is a significant advance in the art in that the device disclosed therein permits a heavy power saw, such as a table saw to be transported to or from a jobsite on roller wheels in the manner of a conventional handtruck. The saw can then be used with the saw stand in a collapsed position (e.g., low to the ground) or in a raised position at table height. This saw stand has a built-in feature that enables the unit to stand in the vertical position with the saw attached. This creates ease in transporting the unit to and from the workplace, i.e., in elevators, truck beds, etc. Also built into the design is the ability to use the saw in the horizontal stowed position for hardwood floor installers, etc.
One disadvantage of this prior art design, as well as other prior art designs discussed above, is that when the saw stand is in the extended or raised position, a significant part of the load is borne by the wheels. The inventor herein has previously invented multi-wheel work benches including a general configuration of a main body and two lateral, extendable infeed/outfeed tables (e.g., U.S. Design Pat. No. D491,709 issued Jun. 15, 2004, title “WORK BENCH,” and U.S. Design Pat. No. D535,490 issued Jan. 23, 2007 titled “WORK BENCH”). While these work benches are well adapted for indoor use on smooth floors (e.g., shop floors), they may transmit induced vibrations from a power tool thereon to a work shop floor through wheels. On a smooth, flat surface (e.g., a garage floor, hardwood floors, etc.) vibrations from the saw tend to cause minor movement in the wheels, thus allowing undesirable vibrations to become amplified through positive feedback and reverberate through the saw stand. More significantly, loads placed on the infeed/outfeed tables tend to exacerbate torque applied at the wheels due to the moment effect of the tables on the cart, causing the cart to tip.
The inventor herein addressed that need for a mobile, collapsible power tool stand that can roll on wheels, but that also lifts the saw stand off the wheels when erected or extended in his pending application Ser. No. 11/888,378 filed Jul. 31, 2007, the disclosure of which is herein incorporated by reference. In that disclosure, an extended foot portion is provided adjacent to the wheels at the end of the stand allowing the stand to be raised off its two wheels when deployed. However, for less mobile applications (e.g., a workshop environment with a smooth floor) where tool and work carts employing four wheels are used satisfactorily, a self-jacking anti-tip solution for a mobile tool cart has evaded the ingenuity of the prior art. Thus, a need exists for a self-jacking work cart of the type having four wheels so as to isolate vibrations and other movements from tools, saws, etc. on the cart, and working actions on the cart infeed/outfeed tables from tipping the cart or moving the cart about the floor by virtue of the low frictional engagement therewith due to the wheels.